After more than five years of construction, San Mateo’s upgraded Wastewater Treatment Plant was unveiled in a ribbon-cutting ceremony. It is the largest infrastructure project in San Mateo’s history, and developers say it’s one of the most sustainable wastewater treatment facilities in the country. … The plant is part of San Mateo’s $1 billion Clean Water Program, an initiative that was launched in 2015 in response to a cease and desist order the city received mandating sewer system improvements to prevent overflow into the San Francisco Bay.